Maternal body mass index and hypotension in patients undergoing caesarean section under spinal anaesthesia at Kenyatta national hospital.

Abstract

Pregnancy and obesity are both independently associated with increased anaesthetic risks. This study sought to determine the incidence and severity of hypotension in patients with a raised BMI undergoing CS under spinal anesthesia in a tertiary hospital in Kenya. This study was carried out between the months of January and April 2015 at the Kenyatta National Hospital, Nairobi Kenya. The objective was to determine and compare the frequency and severity of hypotension in parturients with high maternal BMI (> 25) and those with normal BMI (18.5-24.9) during spinal anaesthesia. We designed a comparative cross sectional study. The study population included all women of childbearing age undergoing caesarean section in KNH. The sample population was divided into two groups. One group was women who were obese BMI > 30 (74 women) and the other group was women with normal BMI i.e. 18.5-24.9. (76 women) The outcome of interest was the development of hypotension during spinal anaesthesia and its severity and a comparison was made between the two groups. The incidence of hypotension in the obese group of women was 83.8% as compared to those with normal BMI whose incidence was 69.7%. Obese patients were more likely to have moderate or severe hypotension (27% and 18.9%, respectively) compared to normal weight (11.8% and 5.3%, respectively) patients undergoing caesarean delivery under spinal anaesthesia and on average the blood pressure reduced by 0.6% from the baseline level for each unit increase in BMI. There was no significant difference in the fluid volumes used intra-op between the two groups and neither did it differ with the severity of hypotension. (p = 0.513) Both groups of patients in our study received boluses of ephedrine when they had hypotension. There was a significant association between ephedrine dosing and correction of hypotension (p < 0.001). The obese group had moderate and severe hypotension necessitating higher doses of the vasopressors. In conclusion the study showed a higher incidence of hypotension in obese parturient women with an average blood pressure reduction of 0.6% from the baseline level for each unit increase in BMI. There was no significant difference in the fluid volumes used intra-op between the two groups. Ephedrine was mainly used to correct hypotension with higher doses required in the obese patients.